It comes as coalition-backed forces close in on the IS stronghold.
Despite the advance, there is increasing criticism of the casualties inflicted by coalition forces in both Syria and Iraq.
United Nations war-crimes investigators say intensified coalition air strikes have killed at least 300 civilians in the northern Syria city of Raqqa since March.
The Syrian Democratic Forces, or SDF, a group of Kurdish and Arab militias backed by the United States-led coalition, began an assault to retake the city from IS a week ago.
The chairman of the United Nations Commission of Inquiry for Syria says the commission is deeply concerned about the rising civilian toll from the air strikes on IS-controlled areas.
And Paulo Pinheiro says the number being driven from their homes is a big concern as well.
“We note, in particular, that the intensification of air strikes which have paved the ground for an SDF advance in Raqqa has resulted not only in staggering loss of civilian life but has also led to 160,000 civilians fleeing their homes and becoming internally displaced.”
A commissioner on the independent panel, Karen Abuzayd, says it has documented 300 deaths from coalition air strikes in three months, most of them in the village of al-Mansoura.
“We’ve documented the deaths just caused by the coalition air strikes only, and we have about 300 deaths, 200 in one place, in al-Mansoura, one village. So, those are the figures that we have been able to record.”
The UN investigators do not have access to Syria.
Instead, their data is collected by interviewing survivors and witnesses in neighbouring countries or by Skype with those still in Syria.
The London-based monitoring group Airwars says the figure of 300 deaths is nearly twice as high as the deadliest strike in the Iraqi city of Mosul, (MO-zul) which the coalition has admitted to.
Sahr Muhammedally is the Middle East and North Africa director for the Washington-based Centre for Civilians in Conflict.
She has told SBS she is concerned with the coalition conducting operations in densely populated areas in both Iraq and Syria.
“The numbers that the coalition has put out is a little bit over 400 since 2014, both in Iraq and Syria, which I think is incredibly low, given the amount of munitions and bombs that have been dropped, and especially since the campaign intensified in October of 2016. Other external organisations are reporting much higher numbers of civilian harm attributed, like in the thousands. I think Airwars has reported around 3,000 or so.”
Airwars recently reported data from the coalition’s Operation Inherent Resolve showed a 34 per cent jump in munitions dropped by coalition forces in May alone.
Most of that was said to be around Raqqa.
Meanwhile, data released by Australia’s Operation Okra shows Australian planes dropped a record 119 munitions on IS in the month of May, all in Iraq.
The figures come as US defence secretary James Mattis has recently announced an accelerated coalition strategy.
“The bottom line is we are going to move in an accelerated and reinforced manner, throw them on their back foot. We have already shifted from attrition tactics, where we shove them from one position to another, in Iraq and Syria, to annihilation tactics, where we surround them. Our intention is that the foreign fighters do not survive the fight.”
But Sahr Muhammedally says the coalition needs to address the issue of civilian casualties as it moves forward.
“Sometimes, it’s not really the numbers. It’s about what the coalition is doing when these numbers are being reported, to assess, to see how they can change their tactics. And as the campaign is being undertaken in very densely populated areas, where the civilians are not being allowed to move, the likelihood of civilian casualties is just almost a given. So they really need to slow down and assess how slowly, block by block, they’re going to be engaging ISIS and trying to allow civilians to move to safer areas.”